(1) Field of the Invention
This invention relates to a method and an apparatus for continuously producing an emulsion containing a dispersed liquid phase in a continuous liquid phase. More particularly, the invention concerns a method and an apparatus for producing an emulsion continuously by mixing atomized particles of a dispersed phase liquid, which are sprayed from a rotary atomizing head, with a continuous phase liquid flowing down in the form of a thin filmy stream within an emulsifying vessel.
(2) Description of the Prior Art
There have heretofore been employed various methods for preparing emulsions by mechanically shaking a mixture of continuous and disperse phase liquids, which however have a serious problem that it is difficult to control the particle size of the dispersed phase liquid, often resulting in an unduly large particle size distribution.
On the other hand, there have been proposed methods for preparing an emulsion in a continuous and stable manner without the above-mentioned problem, including U.S. Pat. No. 4,237,028 which discloses a method for preparing an emulsion by atomizing a disperse phase liquid electrostatically by flowing the liquid over the edge of a flat blade which is applied with a high voltage, forming a spray of atomized particles of the disperse phase liquid against streams of a continuous phase liquid flowing down along channels formed on a carrier.
However, the method of the above-mentioned U.S. patent has a number of drawbacks as well. More specifically, the use of a flat blade imposes certain limits on the properties of the disperse phase liquid to be atomized depending upon such as the width and angle of inclination of the blade, in some cases making the electrostatic atomization utterly difficult with particular kinds of disperse phase liquid, in addition to the difficulty of atomizing a large quantity of the disperse phase liquid. There is a further problem that it is difficult not only to attain uniform atomization of the disperse phase particles but also to control the particle size, due to varying the voltage to be applied to the blade being the sole factor for controlling the particle atomization. Besides, the channels which are provided on the carrier for the continuous phase liquid become an obstacle to the formation of a uniform thin filmy stream of the continuous phase liquid as required in the production of an emulsion of satisfactory quality. There is a still further problem that the disperse phase liquid which flows down over the blade is easily influenced by variations in viscosity and ambient temperature, in addition to the foregoing drawback of difficulty to control its particle size, resulting in a wide particle size distribution which is detrimental to the production of high quality emulsions.